"Any of the vintage use DD's use 3 phase motors ?"
This caused me to try to think for a moment of one that isn't at least three phase, and I'm coming up empty.
A local dealer dealer just mentioned the Fender x MoFi PrecisionDeck Limited Edition Turntable is in stock.
“Differences between turntables often comes down to the cartridge.” The same cartridge will sound different in a different tonearm on a different turntable. The same turntable will sound different with a different tonearm and cartridge. These variables are not trivial. And your general statement leaves out the tonearm entirely.
Three phase is easily obtained by driving a 3 phase motor with a 1 phase, and tapping the 3 phase power inputs. Viola, 3 phase power. But 3 phase is more complicated than it looks, and so is better left alone.
But it’s pretty much academic if you have a two phase motor with a quadrature motor controller, that is, producing sine and cosine. Then run the motor with sine and whatever mixture of sine and cosine gives the smoothest results. Pretty much the same performance as 3 phase with less grief.
And must agree with Lew on this. Turntable is most important, tonearm next, cartridge last. IMO. Anyway, you can’t get close to top performance from, say, a 10K cartridge with anything less than a first class TT and tonearm, say 50K or preferably more. My own tonearm adjusts azimuth to less than 1 minute of arc, and just this evening I found myself changing over a +/- 2 minute range with clearly audible results. Not many arms can do this, and unless they can, cartridge performance suffers.